LESSON 383 OF 410 · PROJECTS: COMMAND-LINE TOOLS

CLI Tool: grep v3 — Invert Match in Java

Practice

Build the -v flag of the Unix grep command. Given a list of lines and a search pattern, return all lines that DO NOT contain pattern as a substring (case-sensitive). Return the remaining lines (the ones that do not contain the pattern), in their original order, joined by newline characters (\n).

Function signature:

public String grepInvert(List<String> lines, String pattern)

Example:

Input:
pattern = "err"
lines = ["error", "ok", "another error", "fine"]

Output: "ok\nfine"

When printed:
ok
fine

If every line contains the pattern, return the empty string "".

Same as grep v1 but flip the condition: keep lines where !line.contains(pattern).

The full solution:

class Solution {
    public String grepInvert(List<String> lines, String pattern) {
        List<String> result = new ArrayList<>();
        for (String line : lines) {
            if (!line.contains(pattern)) {
                result.add(line);
            }
        }
        return String.join("\n", result);
    }
}

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CLI Tool: grep v3 — Invert Match in Java

Grep V3 in Java